Aqueous cement composition

ABSTRACT

A fresh aqueous cement composition suitable for building purposes is described. It contains, besides a hydraulic cement, a methyl ethyl cellulose ether having a DS methyl of 0.4-2.2, a DS ethyl of 0.05-0.8 and a MS hydroxy-(C 2 -C 3 )-alkyl of 0-2. The celulose ether imparts excellent rheology properties, including a high water-retention combined with a long open time, to the cement composition. A dry blend and a rheology additive containing the cellulose ether are also described.

This application claims priority of PCT Application No. PCT/SE02/02164,filed Nov. 26, 2002, and Swedish Patent Application No. 0104048-4, filedDec. 3, 2001.

The present invention relates to a fresh aqueous cement compositionsuitable for building purposes. It contains a methyl ethyl celluloseether, which imparts excellent rheology properties, including a highwater-retention combined with a long open time, to the cementcomposition.

Non-ionic cellulose ethers, such as methyl cellulose ethers, methylhydroxyethyl cellulose ethers and methyl hydroxypropyl cellulose ethers,are frequently used in fresh cement mortars as a water-retention andthickening agent. The methyl cellulose ethers also improve such rheologyproperties as workability, stability and adhesion. Other commerciallyavailable cellulose ethers for modern cement-based compositions areethyl hydroxethyl cellulose ethers. It is also well known to combine thecellulose ethers with synthetic polymers, e.g. polyacrylamides andpolyvinyl alcohols, in order to further improve the properties of thefresh cement mortars. See for example U.S. Pat. No. 5,234,968.

It is also of essential importance that the fresh cement composition hasan open time necessary for the work to be done in a practical manner anda satisfactory adhesion and that the fresh cement composition, aftercuring, results in a product of good strength.

According to the present invention it has now been found that a fresh,aqueous cement composition containing a hydraulic cement and a methylethyl cellulose ether, having a DS methyl of 0.4-2.2, preferably0.6-1.8; a DS ethyl of 0.05-0.8, preferably 0.1-0.5; and ahydroxy-(C₂-C₃)-alkyl of 0-2, preferably 0.1-1.2; exhibits good rheologyproperties, such as a high water-retention combined with a long opentime, a good adhesion and a high strength of the cured product. Theamount of the methyl ethyl cellulose ether is suitably from 0.05-3%,preferably 0.1-2%, and most preferably from 0.2-1.0, by weight of thedry weight of the fresh cement composition.

The methyl ethyl cellulose ether has advantageously a flocculationtemperature between 55° C. and 85° C., preferably between 60° C. and 80°C., while the viscosity suitably is between 200 mPa·s and 20000 mPa.s,measured in a 1% by weight solution at 20° C. according to BrookfieldLV, spindle 1-4, 12 rpm.

The presence of both methyl and ethyl groups in the cellulose etherprolongs the open time of the fresh cement composition that is availablewithout undue degree of reduction of the adhesion and the strength ofthe cured product. The presence of hydroxyethyl or hydroxypropyl groupsdoes not suppress but normally improves these properties further. Inaddition, the use of the celluloseether in question in the cementcomposition results in an air entrainment that supports an excellentconsistency of the fresh cement composition and a good resistencytowards formation of cracks in the cured product. The cement compositionof the invention has properties, which make them suitable to be used asa cement mortar, such as plaster, joint fillers, floor screeds, grouts,and tile adhesives.

The methyl ethyl cellulose ether disclosed can be produced by reactingan alkali cellulose with methyl chloride, ethyl chloride and optionallyethylene oxide and/or propylene oxide. Suitably the reaction isperformed in the presence of an inert organic reaction medium attemperatures between 60-115° C. in accordance with the principlesdisclosed in the textbook: Ullmann's Encyclopaedia of IndustrialChemistry, Fifth, Completely Revised Edition Volume A5, p 468-474.

According to the invention, the hydraulic cement can be ordinaryPortland cement, low heat Portland cement, white Portland cement, rapidhardening Portland cement, and aluminous cement, or mixtures thereof.Suitably the hydraulic cement contains 75-100% by weight of ordinaryPortland cement or white Portland cement. The hydraulic cement can alsobe combined with 0-25% by weight of lime and/or gypsum. In general, thecement composition also contains fillers, although for certainapplications, such as cement glue for mosaic, the presence of fillersmay not be required or desired. The fillers are usually an inorganicmaterial with a particle size of 5 mm or less. The inorganic material ispreferably selected from the group consisting of silica,calciumcarbonate, different types of dolomite and expanded minerals. Thefillers for use in plasters suitably comprise at least 98% by weight ofparticles having a particle size less than 4 mm, while fillers for tileadhesives, grouts, joint fillers and floor screeds normally comprise atleast 98% by weight of particles having a particle size less than 1.5mm.

According to the invention the cement composition can, besides themethyl ethyl cellulose ether, also contain other additives which affectthe rheology. Examples of such other additives are other polymersconsisting of water-soluble or water-dispersable synthetic organicpolymers resistant to alkali, such as polyvinyl-acetates, polyvinylalcohols, polyacrylamides, copolymers between vinyl acetate and vinylalcohol, copolymers between vinyl acetate, vinyl chloride and vinyllaurate, copolymers between acrylates and methyl methacrylates, anionicor nonionic starch derivates, polymeric plasticizers and mixturesthereof; and clays, such as kaolin, bentonite, attapulgite and mixturesthereof. These additives have normally a thickening effect and improvethe stability of the fresh cement composition and the flexibility of thecured product, thereby reducing the risk of crack formation. A suitablerheology additive for use in a fresh composition according to theinvention comprises 10-100%, preferably 40-90% by weight of a methylethyl cellulose ether according to the invention, 0-90%, preferably10-60% by weight of another polymer consisting of water-soluble orwater-dispersible synthetic organic polymer resistant to alkali, and0-90%, preferably 0-50% by weight of clay.

In addition to the above mentioned components the cement composition canalso contain a number of other ingredients, such as air-entrainingagents, retarders, accelerators, nonpolymeric plasticizers, pigments,colorants and corrosion inhibitors.

A typical fresh cement composition according to the invention contains0.05-3%, preferably 0.1-2% and most preferably 0.2-1%, by dry weight ofthe composition of a rheology additive containing a methyl ethylcellulose ether as defined above,

8-99.5, preferably 12-65% by dry weight of the composition of ahydraulic cement,

0-91, preferably 45-83% by dry.weight of the composition of a fillerhaving a particle size of 5 mm or less,

0-10, preferably 0.05-4% by dry weight of the composition of otheringredients, and

10-60, preferably 15-40% by weight of the fresh cement composition ofwater.

The fresh composition may be prepared by first mixing at least a part ofthe cement with the rheology additive and the other ingredients,whereupon the remaining cement and the filler is added in one or moresteps and thoroughly mixed to a homogeneous dry blend. Just before theactual use of the fresh cement composition a suitable amount of the dryblend is thoroughly mixed with the desired amount of water.

The present invention is further illustrated in the following examples.

EXAMPLE 1

Five cement compositions suitable to be used as a tile fix mortar wereprepared by mixing according to DIN 18156, 400 g of ordinary Portlandcement; 525 g of sand having a particle size of less and 0.5 mm and 75 gof siliceous fluor having a particle size of less than 0.5 mm as afiller; 4 g of any one of the nonionic cellulose ethers according toTable 1 below; and 235 g of water.

TABLE I Nonionic cellulose ethers used in the compositions CompositionsProperty 1 2 A B C DS methyl 1.35 1.35 1.5 1.5 1.6 DS ethyl 0.12 0.12 00 0 MS hydroxyethyl 0.12 0.06 0.12 0.06 0 MS 0 0 0 0 0.2 hydroxypropylViscosity¹⁾, 7830 11800 11500 12400 3720 mPa · s Flocculation 69 67 6868 61 temperature, ° C. ¹⁾Viscosity measured according to Brookfield LV,spindle 1–4, 12 rpm in 1% by weight solution at 20° C.The properties of the cement composition were examined with regard toair content (by density measurements), flow table value (ASTM C280-68),slip (UEAT_(c)), open time measured as tensile strength on non-vitreoustiles (DIN 18156, part 2). The tiles were applied after 0.5 and 10minutes and the tensile strength measured after 28 days. The resultsobtained are shown in Table II below.

TABLE II Performance of the cement compositions Compositions Property 12 A B C Air content, % 15.0 14.1 14.5 13.7 15.8 Flow table 160 159 158157 167 value, mm Slip, mm 1 1 2 2 1 Open time as tensile strength,kg/cm²  0 min 24.8 23.8 24.6 13.9 22.6  5 min 18.1 20.2 10.5 9.8 15.7 10min 12.0 10.8 7.8 8.1 7.1From the results it is evident that the open times during which a hightensile strength are obtainable is essential longer for the cementcompositions 1 and 2 according to the invention than for the comparisoncompositions A, B and C.

EXAMPLE 2

Three cement compositions were prepared according to the formula inExample 1 but the amount of water was increased to 240 g. The nonioniccellulose ethers exhibited the following properties.

TABLE III Nonionic cellulose ethers used in the cement compositionsCompositions Property 3 4 D DS methyl 1.2 1.5 1.8 DS ethyl 0.25 0.25 0MS hydroxyethyl 0.12 0.12 0.12 Viscosity, mPa · s 16900 17700 18900Flocculation temperature, 64.5 61.7 64.6 ° C.The properties of the cement compositions were examined in the samemanner as in Example 1, but with the exception that the air content wasnot measured. The following results were obtained.

TABLE IV Performance of the cement compositions Compositions Property 34 D Flow table value, mm 141 140 138 Slip, mm 2 3 2 Open time as tensilestrength, kg/cm²  0 min 21.7 25.8 21.9  5 min 17.1 23.8 9.8 10 min 7.65.4 0.8The compositions 3 and 4 according to the invention exhibited essentialbetter open times than the comparison composition D.

EXAMPLE 3

Two cement compositions were prepared in accordance with Example 1, butthe water content was adjusted so the cement compositions received aslip between 0.5 mm and 1 mm. Furthermore, two similar cementcompositions were prepared. The difference was that these compositionsas a rheology additive contained a blend of 4 g of any of the celluloseethers and 0.08 g of a polyacrylamide. The rheology additive used in thefour cement compositions are shown in Table V.

TABLE V Rheology additive used in the compositions CompositionsComponents 6 7 E F Cellulose ether, g 4 4 4 4 DS methyl 0.9 0.9 — — DSethyl 0.35 0.35 0.95 0.95 MS hydroxyethyl 0.9 0.9 2.35 2.35 Viscosity,cP 2100 2100 6000 6000 Flocculation, ° C. 70.1 70.1 69 69Polyacrylamide, g — 0.08 — 0.08The air content, slip, flow table value and open time of the four cementcompositions were determined in the same manner as in Example 1.Furthermore, the water-retention was determined according to ASTM C91-71(modified with a funnel diameter of 80 mm and an evacuation for 10minutes). The following results were obtained.

TABLE VI Performance of the cement compositions Compositions Property 67 E F Water addition, g 220 250 225 255 Air content, % 24 20 22 23 Flowtable value, mm 158 164 154 154 Slip, mm 1 0.5 1 0.5 Open time astensile strength, kg/cm²  0 min 21.8 21.1 12.7 12.0  5 min 16.6 12.710.6 6.0 10 min 7.2 6.5 4.3 0.0 Water retention, % 97.1 96.7 97.2 96.1The cement compositions 6 and 7 according to the invention haveessentially better open time property than the comparisons E and F.Water-retention values between 94% and 98% are excellent.

1. A fresh aqueous cement composition comprising a hydraulic cement anda cellulose ether, wherein the composition comprises a methyl ethylcellulose ether having a DS methyl of 0.4-2.2, a DS ethyl of 0.05-0.8and a MS hydroxy-(C₂-C₃)-alkyl of 0-2.
 2. The cement composition ofclaim 1 wherein the methyl ethyl cellulose ether has a DS methyl of0.6-1.8, a DS ethyl of 0.1-0.5 and a MS hydroxy-(C₂-C₃)-alkyl of0.1-1.2.
 3. The cement composition of claim 2 wherein the hydroxyalkylgroup is hydroxyethyl.
 4. The cement composition of claim 2 wherein thehydroxyalkyl is hydroxypropyl.
 5. The cement composition of claim 1wherein the composition contains about 0.05% to about 3% by dry weightof the methyl ethyl cellulose ether.
 6. The cement composition of claim1 wherein the composition comprises about 0.05% to about 3% by dryweight of the methyl ethyl cellulose ether; about 8% to about 99.5% bydry weight of the composition of the hydraulic cement; 0 to about 91% bydry weight of the composition of a filler having a particle size of 5 mmor less; and about 10% to about 60% by weight of the composition ofwater.
 7. The cement composition of claim 6 further comprising about 0to about 10% by dry weight of the composition of an ingredient selectedfrom the group consisting of air-entraining agents, retarders,accelerator, nonpolymeric plasticizers, pigments, colorants, corrosioninhibitors, and mixtures thereof.
 8. The cement composition of claim 6comprising about 0.1% to about 2% by dry weight of the methyl ethylcellulose ether; about 12% to about 65% by dry weight of the compositionof the hydraulic cement, about 45% to about 83% by dry weight of thecomposition of the filler; and about 15% to about 40% by weight of thecomposition of water.
 9. The cement composition of claim 8 furthercomprising about 0.05% to about 10% by dry weight of the composition ofan ingredient selected from the group consisting of air-entrainingagents, retarders, accelerator, nonpolymeric plasticizers, pigments,colorants, corrosion inhibitors, and mixtures thereof.
 10. A dry blendfor use in the preparation of a fresh cement composition, wherein thedry blend comprises (i) about 0.05% to about 3% by dry weight of amethyl ethyl cellulose ether having a DS methyl of 0.4-2.2, a DS ethylof 0.05-0.8 and a MS hydroxy-(C₂-C₃)-alkyl of 0-2; (ii) about 8% toabout 99.5% by dry weight of the composition of a hydraulic cement; and(iii) 0 to about 91% by dry weight of the composition of a filler havinga particle size of 5 mm or less.
 11. The dry blend of claim 10 furthercomprising 0 to about 10% by dry weight of the composition of aningredient selected from the group consisting of air-entraining agents,retarders, accelerator, nonpolymeric plasticizers, pigments, colorants,corrosion inhibitors, and mixtures thereof.
 12. The dry blend of claim10 comprising about 0.1 to about 2% by dry weight of the methyl ethylcellulose ether; about 12 to about 65% by dry weight of the compositionof the hydraulic cement; about 45 to about 83% by dry weight of thecomposition of the filler; and about 0.05 to about 4% by dry weight ofthe composition of an ingredient selected from the group consisting ofair-entraining agents, retarders, accelerators, nonpolymericplasticizers, pigments, colorants, corrosion inhibitors and mixturesthereof.
 13. A rheology additive for use in a fresh cement compositionor dry blend, said rheology additive comprising: (i) about 40 to about98.5% by dry weight of a methyl ethyl cellulose ether having a DS methylof 0.4-2.2, a DS ethyl of 0.05-0.8 and a MS hydroxy-(C₂-C₃)-alkyl of0-2; (ii) about 1.5 to about 60% by weight of a water-soluble orwater-dispersible synthetic organic polymer resistant to alkali; and(iv) 0 to about 50% by weight of clay.
 14. The cement composition ofclaim 1 which additionally comprises (i) about 1.5 to about 60% byweight of a water-soluble or water-dispersible synthetic organic polymerresistant to alkali; and (iv) 0 to about 50% by weight of clay.